The Internet Protocol (IP) multimedia subsystem (IMS) is a standardized architecture for providing multimedia services over any network supporting packet-based communications. IMS can also be extended to circuit-switched networks through appropriate gateways. IMS is configured to provide a centralized service control system across different network architectures. As such, IMS can support multimedia services over any type of access network. These access networks may support fixed or wireless communications, as long as there is a mechanism to support packet-based communications. Further, IMS allows user mobility wherein the multimedia services are available to a subscriber regardless of location, since the multimedia services may be provided over different access networks and at different locations. The types of multimedia services available through IMS are limitless, but include voice over IP (VoIP), push to talk, multi-party gaming, video conferencing, messaging, presence sharing, content sharing, and related services.
IMS generally uses VoIP technology based on a third generation partnership project (3GPP) implementation of the Session Initiation Protocol (SIP). IMS runs over the standard IP. With IMS, the services can be provided to subscribers irrespective of their location, access technology, and terminal. Although the proposed IMS architecture is flexible in providing multimedia services, it is limited in how these services are selected for a given call or session. At the present, the signaling messages used for call or session signaling are the only sources of information that can be used to determine if and when to invoke a multimedia service. Further, given the plethora of available multimedia services, there is a need to aggregate multimedia services in a manageable fashion and invoke these applications in a flexible and efficient manner.